The only company in the United States that tests it's material before it goes into every bottle is Glucorell R. You should also be aware that taking r-ala without supplementing biotin will lead to depletion of biotin in your body. That's why Glucorell R has biotin in every capsule. Glucorell was the first r-ala in the US. It's sad that everyone that attempts to copy it, like those other brands, seems to think that the purity does matter. This is a bad mistake. The purity determines how effectively the S-ala has been left out. The practices of those companies is just another example of supplement companies sticking whatever some Chinese lab sends them and slapping a label on it without checking it first.
That's why so many people who do try another brand come back to Glucorell R.